C-shaped or u-shaped half-coil, rotor winding with such a half-coil and its manufactuing method

ABSTRACT

Embodiments of the present invention relate to a winding of a rotor for use in rotating electrical machines. More particularly, embodiments of the present invention relate to innovative half-coils used for the winding of the rotor. Moreover, embodiments of the invention pertain to a method for winding a rotor body of an electrical machine. According to embodiments of the invention, half-coils, instead of being manufactured as double hollow conductors, are provided in the form of two single hollow conductors, which are adjacently embedded within a respective slot of the rotor body.

CROSS-REFERENCE TO RELATED APPLICATIONS

This is a national phase U.S. Patent application claiming priority toInternational Application No. PCT/EP2015/057227 having an InternationalFiling Date of Apr. 1, 2015, and EP Application No. 14164161.3 having aFiling Date of Apr. 10, 2014, each incorporated herein in its entiretyby reference.

TECHNICAL FIELD

Embodiments of the present invention relate to a winding of a rotor foruse in rotating electrical machines. More particularly, embodiments ofthe present invention relate to innovative half-coils used for thewinding of the rotor. Moreover, embodiments of the invention pertain toa method for winding a rotor body of an electrical machine.

BACKGROUND

As well known, the conversion of rotating mechanical energy intoelectric energy and vice versa is done by generators and by motors,respectively.

Motors or generators comprise a stator and a rotor. The rotor of themachine rotates inside the stator bore of the stator. For theconventional synchronous machines, the magnetic field is excitedtypically through the current-carrying field windings placed in therotor body made of magnetic material. The combination of the number ofthe rotor poles and the rotational speed in revolutions per minute (rpm)determines the frequency of the rotating magnetic field.

Rotors are generally manufactured with a certain number of coils, eachembedded in the respective slot arranged in the rotor body. Inparticular, each coil comes in the form of a stack of conductors calledturns, generally made of copper.

The rotor winding is made of a plurality of coils, each extendingparallel to the rotor axis along the rotor body. Each coil comesnormally in the form of two opposite symmetric substantially C-shapedhalf-coils. Each half-coil has at its axial ends, two diametricallyopposed radius portions, which form the rotor end winding, each onejoined with the respective radius portion of the opposed half-coil, thusforming a complete rotor coil with all coils making up the rotorwinding.

Typically, the joining of the half-coils in correspondence of the radiusportions is accomplished by a brazing process, wherein the turns to bejoined, located at both ends of the coil, are individually or in stacksheated to the braze temperature after the brazing alloy is positioned inthe joint area.

The turns used for the half-coils are usually hollow, having one or twochannels running throughout their axial length. Such a channel is neededin order to guide a fluid within the conductor for cooling purposes,since the current flows generate heat which must be removed from themachine.

The conductors usually come in the form of single hollow conductors,having a sole axial channel, or double hollow conductors, having acouple of channels running internally. The hollow conductors can besolidly formed or made from C-Sections (single hollow conductor) orE-Sections (double hollow conductor). The choice of designing the rotorwinding with single-hollow conductors or double-hollow conductors mostlydepends on the required power that must be delivered and the requiredmechanical strength of the coils. Double-hollow conductors are usuallyinstalled for high-power machines, while single-hollow conductors can besuitable for machines of less power.

However, the manufacturing of the double-hollow conductors, required forhigh-power machines, is usually more complex and time-consuming comparedto the production of the single-hollow conductors, which results in ahigher manufacture cost. A double-hollow conductor is mechanicallystronger and deforms less compared to a single hollow conductor of thesame width.

Furthermore, it is known practise to manufacture half-coils wherein theradius portions are brazed at its corners.

Corner brazing is usually avoided; instead, the rotor winding, in whichthe half-coils have radius end portions obtained by bending, may bebeneficial. In fact, the brazing process, besides being a time-consumingand expensive process, cannot fully guarantee during the whole life ofthe machine the integrity and stability of the rotor winding.

However, a suitable solution for replacing corner brazed rotor coils ischallenged by limited axial space underneath the retaining ring.

On rotors where the original design has brazed joints (corner brazing orbrazed-on bow section) in the rotor end winding, a rewind solutionnecessarily has to have brazed corner joints as well, in order to meetthe spatial constraints, i.e. the available space in axial directionunder the retaining ring. In fact, bent corners tend to occupy moreroom, in the axial direction, with respect to brazed corner designs,where a bow section with different/smaller section is brazed on to saveaxial space. As a consequence, replacing the old winding with bentcorners in the rotor end winding implies the replacement of the oldretaining ring with a larger one.

Nevertheless, supplying a new retaining ring with larger axial dimensionis not always technically feasible and a disadvantage in terms of pricecompetitiveness may be experienced.

SUMMARY OF THE DESCRIPTION

The object of the present invention is to solve the aforementionedtechnical problems by providing an innovative C-shaped half-coil for thewinding of a rotor body as substantially defined in herein. Furthermore,a method is provided for winding a rotor body as substantially definedherein.

According to embodiments of the invention, which will be described inthe following detailed description only for exemplary and non-limitingpurposes, the C-shaped half-coils, instead of being manufactured asdouble-hollow conductors, are provided in the form of two single-hollowconductors which are adjacently embedded within a respective slot of therotor body.

In this way, the manufacturing process is improved because, as mentionedabove, the production of single-hollow conductors is faster and cheaperversus the production of double-hollow conductors. In an embodiment,this leads to an improved process in the manufacturing of electricalmachines having conductors which require two cooling channels.

Moreover, this solution further improves a rewind process of the rotorbody, providing coils having bent corners (in place of the existing oneshaving brazed corners or brazed-on bow sections without the need ofreplacing the retaining ring).

In fact, as the half-coils are provided in the configuration of twoseparate single-hollow conductors, only one conductor runs all waythrough the bent part of the end winding, while the other one ends afterleaving the rotor body.

It has been demonstrated that such arrangement works at least for theinner coils of the winding, which are shorter and thus have the thermalmargins to reduce the cross section around their end winding portion.

The separate single conductors can be electrically contacted bydifferent contact techniques, such as soldering, friction welding,riveting, screwing, crimping, contact sleeves, contact bridges, contactstrips.

Therefore, according to aspects of the invention, costly andtime-consuming corner brazing can be omitted and broader supplier basetogether with shorter delivery time for single-hollow conductors insteadof double-hollow conductors are achieved.

According to embodiments, a proposed to secure electrical contactbetween adjacent separate single conductors features a radialarrangement utilizing the centrifugal force to facilitate and enhancethe electrical (galvanic) contact between the adjacent upper and lowerlayer conductors lying one above the other forming a turn, thus thejoining (e.g. brazing) of these two adjacent conductors can be spared,meaning less efforts and lower cost owing to without the need of joining(brazing) process, as it will be fully explained in the detaileddescription of embodiments of the invention.

Regarding this radial arrangement, the following aspects need to benoted: sufficiently good contact shall be maintained along all thedefined areas of the conductors; dimensional tolerances shall beprevented from varying due to deformation during e.g. assembly andpossible axial moving shall be avoided due to vibration.

Moreover, joining the conductors of one layer in the configuration topto bottom together to form a turn, the winding is subjected to lessvibration during operation, and less effort is needed to deal with thejoining points along the conductors, which are a relevant number as suchconductors have lengths usually of several meters.

BRIEF DESCRIPTION OF DRAWINGS

The foregoing objects and many of the attendant advantages of thisinvention will become more readily appreciated as the same becomesbetter understood by reference to the following detailed descriptionwhen taken in conjunction with the accompanying drawings, wherein:

Photo 1 is a perspective view of a winding mounted on a rotor body withbent corners belonging to the state of the art;

FIGS. 2 and 3 are respectively a perspective view and a plant view of aportion of a C-shaped half-coil according to a first embodiment of thepresent invention;

FIGS. 4, 5 and 6 are respectively a perspective view, a developed viewand a cross section view of a portion of a C-shaped half-coil of thefirst embodiment of the present invention according to a variantparticularly configured for rewinding operations;

FIG. 7 shows a developed view of a rotor winding according to anembodiment of the present invention;

FIG. 8 shows a cross-sectional view along a section line A-A′ of FIG. 7;

FIGS. 9 and 10 show respectively a cross section and a perspective viewof a half-coil according to a second embodiment of the presentinvention;

FIGS. 11 and 12 show respectively a perspective view and a plant view ofa portion of a C-shaped half-coil of the second embodiment of thepresent invention according to a variant particularly configured forrewinding operations;

FIG. 13 illustrates a cross section of the half-coil of FIGS. 11 and 12;

FIG. 14 illustrates various alternatives for the bottom layer of thehalf-coil of FIG. 11;

FIG. 15 shows a cross section of a half-coil of FIGS. 11 and 12.

DETAILED DESCRIPTION

With reference to photo 1, it shows a state-of-the-art electricalmachine 1. In particular, the photo 1 shows a view of a rotor bodygenerally indicated with reference 2. The rotor body 2 comprises aplurality of axial slots 3. A state of the art C-shaped half-coil 4′ isembedded in a respective slot 3 of the rotor body 3. The C-shapedhalf-coil 4′ comprises an axial active portion 41′ running through therotor slot 3 and two opposite bent radius winding end portions, whichare positioned out of the slot, at different ends of the rotor body 3.In the photo only the bent portion 42′ is visible at one end of therotor body 3. Each C-shaped half-coil 4′ is joined to a correspondentopposed C-shaped half-coil 5′, as clearly showed in the photo.Half-coils 4′ and 5′ form a complete coil. All coils wound around therotor body 2 make up the rotor winding, generally indicated in the photowith numeral 100.

Still making reference to the half-coil 4′ according to the state of theart, the half-coil 4′ comprises a plurality of stacked conductors,called turns, usually made of copper. Each turn of the stack iselectrically insulated from the adjacent turn belonging to the samehalf-coil.

Making now reference to following FIGS. 2 and 3, it is shown a portionof a C-shaped half-coil 4 according to a first embodiment of the presentinvention in a perspective and developed view, respectively. Inparticular, the C-shaped half-coils comprise an active portion 41,configured to be embedded in a respective rotor slot, and two oppositebent radius winding end portions, of which only one bent portion 42 isvisible in the figure, the other bent portion is positioned at the otherend of the rotor slot correspondingly. The half-coil 4 comprises a stackof turns 5 electrically insulated from each other. Each turn 5 of thestack of turns of the half-coil 4 comprises two separate adjacent singleconductors 6 and 7. Conductors 6 and 7 are electrically connected toeach other in order to assure the flow of current between them. Saiddifferently, the turns 5 are disposed on top of each other whilstconductors 6 and 7 are positioned side by side such to be mechanicallyand electrically in parallel. In an embodiment, each single conductor 6and 7 of turn 5 is a hollow conductor, having an inner cooling channelrunning through its axial development (not visible in the figures).Therefore, the positioning side by side of separate single conductors 6and 7, electrically connected to each other, ensures the samefunctionalities of a state-of-the-art double hollow single conductorwhilst facilitating the manufacturing process.

With reference now to FIG. 4, it is shown a portion of a half-coil 8according to an embodiment, particularly configured for operatingrewinding operations.

The C-shaped half-coil 8 comprises, in a similar manner, an activeportion 81, configured to be embedded in a respective rotor slot, andtwo opposite bent radius winding end portions, of which only bentportion 82 is visible in the figure. The half-coil 8 comprises a stackof turns 5 electrically insulated from each other. Each turn 5 of thestack of turns of the half-coil 8 comprises two separate adjacent singlefirst and second conductors 9 and 10. The term first conductor 9 is alsoreferred to as first straight conductor 9, 31 in this whole disclosure.As described not all of the first conductors 9 of the rotor winding 20are mandatorily designed as straight first conductors 9, 31 however. Thefirst conductors 9 can be designed partially as straight firstconductors 9, 31 without a bended portion, and partially as common firstconductors 9 having a bended portion corresponding to the secondconductors 10, 32, see Fig.7. The first straight conductors 9, 31 areconductors with cut out bended parts. Conductors 9 and 10 areelectrically connected to each other in order to assure the flow ofcurrent between them. In this variant, first conductor 9, which is theouter conductor of turn 5, is a straight conductor having its axial endsprotruding outside the respective rotor slot 3 when embedded within therotor body (not shown), and located in the proximity of respective bentradius portions (in the figure only bent portion 82 is visible). As canbe seen in FIGS. 4, 5, and 11 the first straight conductor 9, 31 abutsthe active straight portion of the second conductor 10, 32 along thewhole length of the first straight conductor 9, 31, and the firststraight conductor 9, 31 ends along the length of the second conductor10, 32. This way, the absence of the outer bent portion of conductor 9running adjacently to the bent portion 82 of conductor 10 allows asubstantial reduction of space required in the axial direction for thepositioning of the related turn. It has been shown that this arrangementcan be established at least for the first inner coils wound on the rotorbody where the limited length of the bent portions (which are joined torespective bent portions of opposite half-coils) still allows thetransit of the current on a single conductor instead of two withoutincurring in overheating problems. See in particular FIG. 1 with theinner coils at the left and the outer coils at the right, or FIG. 7.With particular reference to FIG. 5, the turn 5 further compriseselectrical contact means 11 interposed between adjacent conductors 9 and10. To be more precisely, the electrical contact means 11 creates anelectrical contact between the first straight conductor 9, 31 and thestraight part of the second conductor 10, 32. The electrical contactmeans 11 is established in the area of the active portion 81, as can beseen in FIG. 5. As the first straight conductor 9 is merely arranged atthe side of the adjacent straight part of the second conductor 10, thismeans that the electrical contact means 11 has no contact to the bentradius portion 82 of the second conductor 10. According to thisexemplary non limiting embodiment, such contact means 11 are locatedsubstantially in proximity of the axial ends of the first conductor 9.Alternatively, first and second conductors 9, 10 of turn 5 may be inelectrical contact throughout their length around the rotor body.Different techniques, known to those skilled in the art, may be used inorder to electrically connect the first and second conductors 9 and 10of the turn 5 such as soldering, silvering, friction welding, riveting,screwing, crimping, contact sleeves, contact bridges, contact strips.

With reference to FIG. 6, it is shown a cross-sectional view of aC-shaped half-coil of FIGS. 4 and 5 embedded in a respective rotor slot3. In particular, it is visible the half-coil formed by a plurality ofelectrically insulated turns 5 positioned on top of each other. Eachturn 5, comprises two separate single conductors 9 and 10, positionedside by side and electrically contacted to each other, as specifiedabove. In an embodiment, separate single conductors 9 and 10 are hollowconductors, having a cooling channel running throughout their length.

With reference now to next FIG. 7, it is shown a developed view of arotor winding, generally indicated with reference numeral 20. The rotorwinding 20 comprises the plurality of C-shaped half-coils 8, each oneembedded in a respective rotor slot (not shown) and being joined to arespective opposite half-coil 8′ in order to form the complete winding.As shown, the first inner three half-coils comprises two singleconductors 9 and 10 wherein conductors 9 are straight having axial endsin proximity of bent portions of adjacent conductors 10 such that theroom required for the rotor winding is sensibly reduced because ofabsence of radius portions of single conductors 9. This way, existingrotor winding having brazed corners can be replaced by a new rotorwinding 20 during re-winding operation because of the reduction of axialspace thus achieved. In FIG. 7 it can be seen that the inner threehalf-coils 8 are designed according to an embodiment of the inventionwith first straight conductors 9, 31, and the outer four half coils aredesigned in a common way.

FIG. 8 shows a cross-sectional view along a section line A-A′ of FIG. 8.In particular, the figure depicts the single conductors 10 for the firstinner half-coils 8 as described above. Moreover, the figure shows aretaining ring of the electrical machine generally indicated withreference 300.

With reference now to FIG. 9, it shows a cross-sectional view of aportion of a C-shaped half-coil 12 according to a second embodiment ofthe present invention. Similarly, the half-coil 12 comprises an activeportion 121, configured to be embedded in a respective rotor slot, andtwo opposite bent radius winding end portions, of which only bentportion 122 is visible in the figure. The half-coil 12 comprises a stackof turns 5 electrically insulated from each other. Each turn 5 of thestack of turns of the half-coil 12 comprises two separate adjacentsingle conductors 13 and 14 forming a turn. Conductors 13 and 14 areelectrically connected to each other in order to assure the flow ofcurrent between them. In this second embodiment different from the firstembodiment, the turns 5 are disposed, in pairs, side by side, whilstconductors 13 and 14 are positioned on top of each other such to bemechanically end electrically in parallel. As for the first embodiment,each single conductor 13 and 14 of turns 5 is a hollow conductor, havingan inner cooling channel running through its axial development (notvisible in the figure).

FIG. 10 better shows the arrangement of the turns 5 of half-coil 12. Inparticular, turns 5 are positioned, in pairs, side by side each onecomprising separate single conductors 13 and 14 disposed on top of eachother. Conductors 13 and 14 are in electric contact between each other,as above specified, whilst turns 5 are electrically insulated inbetween. For half-coils having an odd number of turns, a last turn 51 atthe bottom of the stack may be provided according to the firstembodiment, the last turn 51 having single conductors positioned side byside. As it will be described in details with reference to the followingfigures, such arrangement assures a reliable and strong contact betweensingle conductors of the same turn, without the particular need ofinterposing electrical contacting means for letting the flow of current,exploiting centrifugal forces experienced by the rotor coils which aregenerated in the electrical machine during operation.

Making now references to following FIGS. 11 and 12, it is shown aportion of a half-coil 30 according to a variant of the secondembodiment particularly suitable for operating re-winding operations.

More in particular, half-coil 30 comprises, in similar manner, an activeportion 301, configured to be embedded in a respective rotor slot, andtwo opposite bent radius winding end portions, of which only bentportion 302 is visible in the figure. The half-coil 30 comprises a stackof turns 5 electrically insulated from each other. Each turn 5 of thestack of turns of the half-coil 30 comprises two separate adjacentsingle first and second conductors 31 and 32. Conductors 31 and 32 areelectrically connected to each other in order to assure the flow ofcurrent between them. In this variant, first conductor 31 is a straightshorter conductor having its axial ends protruding outside therespective rotor slot when embedded within the rotor body (not shown),and located in the proximity of respective bent radius portions (in thefigure only bent portion 32 is visible). Turns 5 are positioned inpairs, side by side. In the portion of the half-coil illustrated, twoturns are shown, comprising, respectively, first single straightconductor 31 and second conductor 32 and first single straight conductor31′ and second conductor 32′. In an embodiment, the arrangement is suchthat, for each pair of turns positioned side by side, first and secondconductors are disposed on top of each other such that the firststraight conductor 31 abuts on second conductor 32′ of the adjacent turnand second conductor 32 abuts on the first straight conductor 31′.Moreover, in an embodiment, the bent radius portions of second conductor32 are arranged aligned with corresponding bent radius portions ofsecond conductor 32′ of the adjacent turn.

Such arrangement may be beneficial as it allows compacting the roomrequired by the stack of coils without exceeding in the axial direction,and at the same time it allows the particular disposition of havingsingle conductors of each turn disposed on top of each other, thusexploiting the centrifugal forces for establishing a strong contactbetween them for ensuring the flow of current.

FIG. 13 shows a cross sectional view of the half-coil 30 of precedingFIGS. 9 and 10.

With reference to FIG. 14, for half-coils having an odd number of turns,the turn 51 at the bottom of the stack may be provided in the form oftwo single separate conductors positioned side by side, as for the firstembodiment. To enhance the electrical contact, a copper strip 40 may beprovided in different configurations between the two conductors.

Lastly, FIG. 15 shows with more details the principle of theexploitation of the centrifugal forces for ensuring a tight contactbetween single conductors of the same turn. As shown by the increasingsizes of the arrows, centrifugal forces intensify with the distance ofthe turn from the centre of the rotor body 2. The reaction to thecentrifugal forces, which actually keeps conductors in each turn in aforced electrical contact is offered by a rotor slot wedge 110 whichencloses the rotor winding.

Moreover, embodiments of the present invention are also directed, withreference to the described figures, to a method for winding a rotor body2 of an electrical machine 1. The winding operation may also be are-winding, that is removing the existing rotor winding and replacing itwith a new one. The method according to an embodiment of the inventioncomprises embedding in each slot 3 of the rotor body a respectiveconductive C-shaped half-coil, the half-coil comprising an axial activeportion running through the slot parallel to a rotating axis R of therotor body 2, shown in FIGS. 1 and 7, and two opposite bent radiuswinding end portions. The half-coil comprises a stack of turnselectrically insulated from each other, wherein each turn of said stackof turns is provided in the form of two separate single conductors,adjacently positioned along the slot 3 and electrically connected toeach other. According to embodiments, six of the two separate singleconductors comprise a first single conductor which is a straightconductor and a second conductor of said two separate single conductorsis C-shaped comprising two opposite bent radius portions. The firstconductor protrudes out of the rotor body 2 and has its axial endslocated in proximity of respective bent radius portions. In anembodiment, providing half-coils so configured for at least the firstthree inner coils of the winding, the re-winding can be effectedlimiting the required axial space, as detailed above.

According to a first embodiment, the turns of at least one half-coil aredisposed along a radial direction and the first and second conductorsare positioned along a circumferential direction with respect to therotating axis R of the rotor body 2.

According to a second embodiment, the first and second conductors ofeach turn are positioned along a radial direction and the turns of atleast a half-coil are positioned, in pairs, along a circumferentialdirection, such that the first conductor of turn abuts on a secondconductor of adjacent turn, wherein the pairs of turns are arrangedwithin the respective slot along a radial direction.

The method further comprising providing a slot wedge 110 supporting thehalf-coils such that, during operation, first and second conductor arepressed to each other due to centrifugal forces.

Although the present invention has been fully described in connectionwith embodiments, it is evident that modifications may be introducedwithin the scope thereof, not considering the application to be limitedby these embodiments, but by the content of the following claims.

What is claimed is:
 1. A C-shaped half-coil for a rotor body of anelectrical machine, the rotor body comprising axial slots, said C-shapedhalf-coil comprising: an active portion configured to be embeddedthrough the respective rotor axial slot and two opposite bent radiuswinding end portions; a stack of turns electrically insulated from eachother, wherein each turn of said stack of turns is provided in the formof two separate adjacent single conductors electrically connected toeach other; and a first conductor and a second conductor of said twoseparate single conductors, wherein said first conductor is a straightconductor and said second conductor is C-shaped and comprises twoopposite bent radius portions, said first straight conductor having itsaxial ends located in proximity of respective bent radius portions ofsaid second conductor and abut the active portion of said secondconductor.
 2. The C-shaped half-coil according to claim 1, furthercomprising electrical contact means positioned lengthwise between saidfirst and second conductors, said electrical contact means being locatedsubstantially in proximity of the axial ends of said first conductor andthe active portion of said second conductor.
 3. The C-shaped half-coilaccording to claim 2, wherein said electrical contact means comprises atleast one of: soldering; silvering; friction welding; riveting;screwing; crimping; contact sleeves; contact bridges; and/or contactstrips.
 4. The C-shaped half-coil according to claim 1, wherein saidseparate single conductors are hollow conductors.
 5. The C-shapedhalf-coil according to claim 1, wherein said turns of said stack ofturns are disposed on top of each other and said first and secondconductors are positioned side by side.
 6. The C-shaped half-coilaccording to claim 5, wherein said first conductor of turn abuts on saidsecond conductor of an adjacent turn, said pair of turns being arrangedon top of each other.
 7. The C-shaped half-coil according to claim 6,wherein said bent radius portions of said second conductor of turn arearranged in alignment with corresponding bent radius portions of saidsecond conductor of said adjacent turn.
 8. An electrical machine,comprising a half-coil according to claim
 1. 9. A method for winding arotor body of an electrical machine, the rotor body having a pluralityof slots, the method comprising: embedding in each slot a respectiveconductive C-shaped half-coil, said half-coil comprising: an axialactive portion running through said slot parallel to a rotating axis Rof the rotor body and two opposite bent radius winding end portions; anda stack of turns electrically insulated from each other, wherein eachturn of said stack of turns of at least one half-coil is provided in theform of two separate single conductors, adjacently positioned along theslot and electrically connected to each other, wherein for each turn ofsaid turn stack of a least one half-coil a first single conductor ofsaid two separate single conductors is a straight conductor and a secondconductor of said two separate single conductors is a C-shaped conductorcomprising two opposite bent radius portions, the first conductor havingits axial ends located in proximity of respective bent radius portionsand abut the active portion of the said second conductor.
 10. The methodfor winding a rotor body according to claim 9, wherein the firstconductor is arranged to be protruding out of the rotor body.
 11. Themethod for winding a rotor body according to claim 9, wherein said turnsof said stack of turns of at least one half-coil are disposed along aradial direction and said first and second conductors are positionedalong a circumferential direction with respect to the rotating axis R ofthe rotor body.
 12. The method for winding a rotor body according toclaim 9, wherein said first and second conductors are positioned along aradial direction and said turns of at least half-coil are positioned, inpairs, along a circumferential direction, such that the first conductorof turn abuts on a second conductor of an adjacent turn, said pairs ofturns being arranged within the respective slot along a radialdirection, the method further comprising providing a slot wedgesupporting said half-coils such that, during operation, first and secondconductors are pressed to each other due to centrifugal forces.
 13. Themethod for winding a rotor body according to claim 10, wherein saidturns of said stack of turns of at least one half-coil are disposedalong a radial direction and said first and second conductors arepositioned along a circumferential direction with respect to therotating axis R of the rotor body.
 14. The method for winding a rotorbody according to claim 10, wherein said first and second conductors arepositioned along a radial direction and said turns of at least half-coilare positioned, in pairs, along a circumferential direction, such thatthe first conductor of turn abuts on a second conductor of an adjacentturn, said pairs of turns being arranged within the respective slotalong a radial direction, the method further comprising providing a slotwedge supporting said half-coils such that, during operation, first andsecond conductors are pressed to each other due to centrifugal forces.